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Issue No. 17, Article 3/July 21, 2006

An Inventory of Field Crop Insect Issues in the Midwest

On July 18, extension entomologists from Illinois, Indiana, Iowa, Michigan, Minnesota, Nebraska, Ohio, and Wisconsin convened during a teleconference to share information about insect situations and issues in their respective states. A synopsis of the reports follows:

Illinois (Mike Gray, Kevin Steffey)

  • Reports continue of large numbers of western corn rootworm adults in some areas, as well as extensive rootworm larval damage in some fields.
  • Japanese beetles continue to generate concern in both corn and soybean fields (what else is new?). There are some reports of green June beetles, described by one person as "Japanese beetles on steroids." These relatives of Japanese beetles (both are in the family Scarbaeidae) do not cause problems in field crops, but their sheer size captures attention. Type "green June beetle" into a Google search to find some excellent photos of the green and gold pests.
  • One report of large numbers of woollybear caterpillars clipping silks in a cornfield in Iroquois County. This observation should be filed away for future reference because yellow woollybears have caused significant defoliation of soybean in the past.
  • Soybean aphids are present in many fields but in low numbers. Refer to the more detailed article in this issue of the Bulletin.
  • According to Kevin Black, entomology and plant pathology specialist with Growmark in Bloomington, numbers of bean leaf beetles in southern Illinois soybean fields (south of Mt. Vernon) are larger than he has observed in recent years, although still below threshold levels. Kevin also noted symptoms of virus infection in some of the fields.
  • Also according to Kevin Black, numbers of green stink bugs (adults, nymphs, and eggs) are large in some soybean fields in southern and western Illinois. Although often overlooked, green stink bugs can cause significant yield losses when they feed on soybean pods. Their numbers bear watching.

Indiana (Christian Krupke)

  • Lots of reports of corn rootworm larval damage, including reports that some rootworm control products failed to protect the roots from damage.
  • Western bean cutworm moths are being captured in pheromone traps at almost all sites where they have been installed in 2006.
  • Numbers of Japanese beetles are large in southern Indiana.
  • Soybean aphids are few and far between, with no reports of densities approaching the economic threshold.

Iowa (Marlin Rice)

  • Significant numbers of western bean cutworm moths are being captured in pheromone traps, with the flight expected to continue into August. Scouts are beginning to find western bean cutworm egg masses.
  • Larger numbers of Japanese beetles than usual in central Iowa.
  • Very little is happening in the world of soybean aphids, although a few fields in northwestern Iowa have been treated with insecticides.

Michigan (Chris DiFonzo)

  • Lots of reports of corn rootworm larval damage in both corn planted after corn and corn planted after soybean.
  • Have been "awash" in grubs during the past two years. Also, there are a lot of Japanese beetles, which may pose a threat to late-planted corn. However, the diverse cropping landscape in Michigan offers more choices for Japanese beetles.
  • Virtually no soybean aphid activity to report.

Minnesota (Ian MacRae)

  • 2006 has been a "banner year" for aphids in small grains, sugar beets, and soybean. Soybean aphids have been more prevalent in the northwestern cropping areas in Minnesota than in the larger acres of soybean in southern and central Minnesota. Many fields of soybean have been treated with insecticides.

Nebraska (Bob Wright)

  • Entomologists at the University of Nebraska have received more reports of corn rootworm larval damage the past couple of years than in immediately preceding years, especially in corn planted after soybean in northeastern Nebraska, where they suspect extended diapause in northern corn rootworms.
  • Captures of western bean cutworm moths in pheromone traps have exceeded 1,000 per night near Clay Center (south-central Nebraska).
  • Soybean aphids are beginning to show up in soybean fields, although numbers are relatively small.
  • Twospotted spider mites are showing up in fields in areas of Nebraska that have been hot and dry.
  • A few isolated reports of aphids (cowpea aphids, spotted alfalfa aphids) in alfalfa.

Ohio (Ron Hammond)

  • Western bean cutworms have been captured in Ohio for the first time, including at sites along the Ohio-Indiana border.
  • Soybean aphids are hard to find in most soybean fields.
  • Numbers of potato leafhoppers are large in alfalfa fields.

Wisconsin (Eileen Cullen)

  • Corn rootworm larval pressure is heavy in many fields, including some extensive damage in corn planted after soybean in south-central and southeastern Wisconsin. The distribution of the variant western corn rootworm seems to be creeping northward.
  • A few captures of western bean cutworm moths in pheromone traps.
  • Not many reports of Japanese beetle problems.
  • Numbers of soybean aphids are small in most areas, although at least three fields have been treated with insecticides.
  • One report of a twospotted spider mite infestation in Jefferson County, although the infestation was not large enough to require a miticide application.
  • Infestations of potato leafhoppers in alfalfa are significant in some areas.

This inventory is intended to provide a snapshot of insect issues around the Midwest. As always, please contact any of us if you have information to share.--Kevin Steffey and Mike Gray

Authors:
Kevin Steffey
Mike Gray

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